Production method of low-cost high-quality flux-cored wire steel

Abstract

The invention relates to a production method of low-cost high-quality flux-cored wire steel, and belongs to the technical field of flux-cored wire steel production.The production method comprises the steps that after a steel variety is subjected to blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, molten steel refining treatment and continuous casting blank forming, the finish rolling temperature of finish rolling is controlled to be 760-840 DEG C, the hot rolling laminar cooling mode is rear-section cooling, and the hot rolling temperature is controlled to be 760-840 DEG C; the curling temperature is controlled to be 630-670 DEG C; the deformation quantity is controlled between 60% and 75% through acid rolling treatment; the continuous annealing treatment is controlled as follows: the heating temperature is 820 + / -15 DEG C, the soaking temperature is 820 + / -15 DEG C, the slow cooling temperature is 670 + / -10 DEG C, the rapid cooling plate temperature is 450 + / -10 DEG C, and the cold rolling annealing time is greater than or equal to 3 minutes. By changing the finish rolling temperature, the cooling mode, the coiling temperature, the acid rolling process and the continuous annealing process, a flux-cored wire steel product with the large and uniform ferrite grain size, the yield strength smaller than 200 Mpa and the elongation larger than 48% is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of flux-cored welding wire steel production, and mainly relates to a method for producing low-cost and high-quality flux-cored welding wire steel. The method of the invention can effectively improve the microstructure of flux-cored welding wire steel, solve the problems of small and uneven grain size, high yield strength and low elongation of flux-cored welding wire steel, reduce customer quality complaints, and meet customer needs. Background Art

[0002] Welding wire has been widely used in many fields such as ships, rail vehicles, automobiles, engineering machinery, marine engineering, aerospace, etc. Flux-cored welding wire steel is the main raw material of welding wire, and the market demand for flux-cored welding wire steel is very large. Welding wire factories have higher and higher requirements for the quality of flux-cored welding wire steel. The product quality of flux-cored welding wire steel has a great impact on the cost and production efficiency of welding wire factories. The quality of flux-cored welding wire steel is directly related to the use effect of welding wire products.

[0003] Flux-cored welding wire steel customers require materials with good drawing properties. At present, the main production method of flux-cored welding wire steel on the market is annealing, but the surface quality control of annealed steel strips is difficult, and it is easy to have problems such as adhesion and color difference. For most steel mills, customers require the use of continuous annealing process to produce flux-cored welding wire steel, but continuous annealing will have problems such as high yield strength, small and uneven grain size and low elongation.

[0004] The quality of flux-cored welding wire steel products is mainly related to the state of the microstructure of the flux-cored welding wire steel. The microstructure of the flux-cored welding wire steel is controlled by chemical composition, finishing rolling temperature, cooling method, coiling temperature, pickling process and continuous annealing process to produce flux-cored welding wire steel products that meet the mechanical properties requirements of customers.

[0005] Generally, the chemical composition requires that the C element be controlled at 0.015% to 0.035%, the Mn element be controlled at 0.16% to 0.26%, the Al element be ≤0.045%, and the rest be Fe and residual elements. The current continuous annealing production process cannot obtain a ferrite structure with a large and uniform grain size, resulting in customers reporting that the strength of the flux-cored welding wire steel is high and the elongation is low during use. The flux-cored welding wire steel currently produced using the continuous annealing production process has uneven and small ferrite grains (high average grain size level, above level 10), high yield strength (yield strength > 200Mpa), and low elongation (elongation < 48%). The high average grain size level, uneven grain size, and low elongation will increase the risk of pull-out fracture during the production of welding wire, seriously affecting the production efficiency of the welding wire factory. The high yield strength will cause serious wear of the welding wire factory's abrasives, frequent replacement of accessories, and increase the cost of the welding wire factory. Summary of the invention

[0006] In order to solve the above problems existing in the prior art, the present invention proposes a low-cost and high-quality production method of flux-cored welding wire steel. By changing the finishing rolling temperature, cooling method, coiling temperature, pickling process and continuous annealing process, a flux-cored welding wire steel product with large and uniform ferrite grain size, yield strength <200Mpa and elongation >48% is obtained.

[0007] The technical solution adopted by the present invention to achieve its purpose is as follows:

[0008] A method for producing low-cost and high-quality flux-cored welding wire steel, wherein the steel is subjected to blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, molten steel refining treatment, and continuous casting into billets, and then hot rolling treatment, acid rolling treatment, and continuous annealing treatment are controlled. The invention mainly controls the finishing rolling temperature, cooling method, coiling temperature, acid rolling process, and continuous annealing process, wherein the finishing rolling temperature is controlled at 760°C to 840°C, so that the welding wire steel is rolled in a high-temperature ferrite region, reducing the rolling load, saving rolling power consumption, and reducing costs. Large-sized ferrite grains with uniform size are obtained.

[0009] Furthermore, the hot rolling laminar cooling mode is changed from uniform cooling in the front section to uniform cooling in the back section, so that the grain growth of the steel strip after finishing rolling is longer.

[0010] Furthermore, the coiling temperature is controlled at 630°C to 670°C to prevent the temperature from being too high so as to cause precipitation of C element in the steel, generate cementite or pearlite, and improve the drawing performance of the flux-cored welding wire steel.

[0011] Furthermore, the pickling process is controlled so that the deformation amount is controlled between 60% and 75%.

[0012] Furthermore, the continuous annealing process is controlled with heating temperature of 820±15°C, soaking temperature of 820±15°C, slow cooling temperature of 670±10°C, rapid cooling plate temperature of 450±10°C, and cold rolling annealing time ≥3 minutes.

[0013] Furthermore, in the hot rolling process, the heating temperature of the ingot is 1240±20°C, the heating time is not less than 150 minutes, the start rolling temperature is above 1100°C, and the total reduction rate is 90%.

[0014] Furthermore, the chemical composition and mass percentage of the steel are C: 0.015% to 0.035%, Si: ≤0.030%, Mn: 0.16% to 0.26%, P: ≤0.015%, S: ≤0.045%, Al: ≤0.045%, and the rest are Fe and residual elements.

[0015] The beneficial effects of the present invention are:

[0016] The present invention improves the finishing rolling temperature, cooling method, coiling temperature, acid rolling process and continuous annealing process. First, the flux-cored welding wire steel is rolled in the high-temperature ferrite zone, and the deformation resistance of the organization is small, so as to achieve the purpose of reducing the rolling load, saving the rolling power consumption, and reducing the cost of the flux-cored welding wire steel; second, the problem of uneven grain size of the flux-cored welding wire steel is solved; third, the problem of small grain size of the flux-cored welding wire steel is solved; fourth, the yield strength of the flux-cored welding wire steel is reduced, the elongation of the welding wire steel is increased, and the problems of frequent wire breakage and high cost in the welding wire factory are solved. The flux-cored welding wire steel produced by the method of the present invention can obtain a product with stable mechanical properties, uniform ferrite organization with an average grain size of less than 9.5, yield strength <200Mpa, and elongation ≥48%.

[0017] Compared with the existing technology, it reduces the rolling load during the hot rolling and finishing of flux-cored welding wire steel, saves rolling power consumption, and reduces roller wear. At the same time, it effectively improves the organizational state of flux-cored welding wire steel, reduces yield strength, and increases elongation. It solves the problem of frequent wire breakage in downstream customers' welding wire factories, improves production efficiency, and wins recognition and approval from customers. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the metallographic structure diagram of flux-cored wire steel.

[0019] Figure 2 It is the stress-strain curve of final rolling temperature. DETAILED DESCRIPTION

[0020] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0021] Example 1

[0022] A method for producing low-cost and high-quality flux-cored welding wire steel is provided, wherein a steel having a chemical composition of C: 0.0177%, Si: 0.015%, Mn: 0.17%, P: 0.011%, S: 0.005%, Al: 0.029%, and the rest being Fe and residual elements, is subjected to blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, molten steel refining treatment, continuous casting into billets, and then hot rolling treatment, acid rolling treatment and continuous annealing treatment, wherein parameter control is shown in Table 1. Then, the steel is subjected to flattening treatment and oil coating packaging to obtain low-cost and high-quality flux-cored welding wire steel.

[0023] Example 2

[0024] A method for producing low-cost and high-quality flux-cored welding wire steel is provided, wherein a steel having a chemical composition of C: 0.0181%, Si: 0.018%, Mn: 0.16%, P: 0.014%, S: 0.005%, Al: 0.031%, and the rest being Fe and residual elements, is subjected to blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, molten steel refining treatment, continuous casting into billets, and then hot rolling treatment, acid rolling treatment and continuous annealing treatment, wherein parameter control is shown in Table 1. Then, the steel is subjected to flattening treatment and oil coating packaging to obtain low-cost and high-quality flux-cored welding wire steel.

[0025] Example 3

[0026] A method for producing low-cost and high-quality flux-cored welding wire steel is disclosed, wherein a steel variety having chemical composition of C: 0.0196%, Si: 0.011%, Mn: 0.18%, P: 0.010%, S: 0.006%, Al: 0.018%, and the rest being Fe and residual elements, is subjected to blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, molten steel refining treatment, continuous casting into billets, and then hot rolling treatment, acid rolling treatment and continuous annealing treatment, wherein parameter control is shown in Table 1. Then, the steel variety is subjected to flattening treatment and oil coating packaging to obtain low-cost and high-quality flux-cored welding wire steel.

[0027] Example 4

[0028] A method for producing low-cost, high-quality flux-cored welding wire steel, wherein a steel type having a chemical composition of C: 0.0188%, Si: 0.008%, Mn: 0.19%, P: 0.014%, S: 0.009%, Al: 0.011%, and the rest being Fe and residual elements, is subjected to blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, molten steel refining treatment, and continuous casting into billets, and then hot rolling treatment, acid rolling treatment, and continuous annealing treatment are performed, wherein the parameter control is shown in Table 1. Then, the low-cost, high-quality flux-cored welding wire steel is obtained through flattening treatment and oil coating packaging. The metallographic structure diagram of the flux-cored welding wire steel of this embodiment is shown in Table 1. Figure 1 (b).

[0029] Example 5

[0030] A method for producing low-cost and high-quality flux-cored welding wire steel is disclosed, wherein a steel having a chemical composition of C: 0.0236%, Si: 0.012%, Mn: 0.23%, P: 0.015%, S: 0.002%, Al: 0.026%, and the rest being Fe and residual elements, is subjected to blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, molten steel refining treatment, and continuous casting into billets, and then hot rolling treatment, acid rolling treatment, and continuous annealing treatment are performed, wherein parameter control is shown in Table 1. Then, the steel is flattened and oil-coated and packaged to obtain low-cost and high-quality flux-cored welding wire steel.

[0031] Example 6

[0032] Improve the production method of pre-flux cored welding wire steel, the chemical composition of steel is C: 0.0188%, Si: 0.008%, Mn: 0.19%, P: 0.014%, S: 0.009%, Al: 0.011%, the rest is Fe and residual elements, after blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, molten steel refining treatment, continuous casting into billets, hot rolling treatment, acid rolling treatment and continuous annealing treatment, wherein,

[0033] The hot rolling process control includes: controlling the finishing rolling temperature at 908°C, the cooling method is front-end cooling, and the coiling temperature is controlled at 699°C;

[0034] Pickling treatment control includes: deformation control at 75%;

[0035] The continuous annealing treatment control includes: heating temperature 829℃, soaking temperature 825℃, slow cooling temperature 702℃, rapid cooling plate temperature 458℃, and cold rolling annealing time 4.7min.

[0036] Then, it is flattened and oiled to obtain flux-cored welding wire steel. Figure 1 (a).

[0037] The mechanical properties of the low-cost, high-quality flux-cored welding wire steel obtained above were tested, and the results are shown in Table 1.

[0038] Table 1

[0039]

[0040] Combination Figure 1 Grain size changes, Figure 2 From the stress-strain curve and the mechanical property data in Table 1, it can be seen that before the improvement, the average grain size of Example 6 is above 10, the yield strength is 235-250Mpa, the tensile strength is 320-340Mpa, and the elongation is 40-48%. After the improvement of the method of the present invention, the structure of the flux-cored welding wire steel produced is ferrite, the average grain size is ≤9.5, the yield strength is below 200Mpa, and the elongation is above 48.5%.

Claims

1. A method for producing low-cost and high-quality flux-cored welding wire steel, wherein the steel is smelted in blast furnace molten iron, pre-treated with molten iron desulfurization, smelted in converter molten steel, refined, and continuously cast into billets, and then subjected to controlled hot rolling, pickling, and continuous annealing, wherein: The hot rolling process control includes: controlling the finishing rolling temperature at 760℃~840℃, the hot rolling laminar cooling method is the rear section cooling, and the curling temperature is controlled at 630℃~670℃; Pickling treatment control includes: deformation control between 60% and 75%; Continuous annealing treatment control includes: heating temperature 820±15℃, soaking temperature 820±15℃, slow cooling temperature 670±10℃, rapid cooling plate temperature 450±10℃, cold rolling annealing time ≥3min.

2. The method for producing a low-cost and high-quality flux-cored welding wire steel according to claim 1, characterized in that: In the hot rolling process, the heating temperature of the ingot is 1240±20°C, the heating time is not less than 150 minutes, the start rolling temperature is above 1100°C, and the total reduction rate is 90%.

3. The method for producing a low-cost and high-quality flux-cored welding wire steel according to claim 1, characterized in that: The chemical composition and mass percentage of the steel are C: 0.015% to 0.035%, Si: ≤0.030%, Mn: 0.16% to 0.26%, P: ≤0.015%, S: ≤0.045%, Al: ≤0.045%, and the rest are Fe and residual elements.

Images